Techniques for improving the covering power of silver halide in silver halide photographic materials have been variously investigated from the viewpoint of saving the amount of silver used for these photographic materials. A method of using tabular silver halide grains is known as one of these techniques.
The conventional method of using tabular silver halide grains may be excellent in improving the covering power of the silver halide but the method is not always satisfactory due to the disadvantage that the photographic materials using the tabular silver halide grains tend to be influenced by the development processing conditions used.
Hitherto, it is known to incorporate various additive such as stabilizers, antifoggants, etc., in ordinary silver halide photographic materials to minimize the development processing dependence of the photographic materials. These additives include for example, nitrobenzimidazoles, mercaptothiazoles, benzotriazoles, nitrobenzotriazoles, mercaptotetrazoles, etc., as described in U.S. Pat. Nos. 3,954,474 and 3,982,947; Japanese Patent Publication No. 28,660/'77, etc. However, with silver halide photographic materials containing tabular silver halide grains, these additives do not restrain the deviation of gradation of the photographic materials due to change in Br.sup..crclbar. ion concentration in the developer or in high-temperature processing although the increase of fog in high-temperature processing may be restrained.
That is, high-temperature development, in particular high-temperature rapid processing using an automatic processor for efficiently performing the development of silver halide photographic materials is known in the art and such a process is employed to process various kinds of photographic materials with good effect. However, since photographic materials are processed at a high temperature in the process, the physical strength of the emulsion layers of the photographic materials must be increased to prevent the emulsion layers from becoming brittle by the pressure of rollers and belts of the automatic processor. Accordingly, measures must be taken to increase the physical strength of the emulsion layers of the photographic materials as the development progresses in a developer to keep the high strength of the emulsion layers during processing. For the purpose, a processing method which is performed with the addition of an aldehyde series hardening agent to a developer has been proposed. According to the method, the overall processing time is shortened by high-temperature processing and the purpose of rapid processing is attained to some extent. However, when the development process is performed using a developer containing, for example, an aldehyde, in particular an aliphatic dialdehyde, the formation of fog becomes severe. This tendency is increased as the temperature at which the developer is used increases and the developing time is longer. The formation of fog caused by such an aldehyde can be prevented to some extent by using a strong antifoggant such as benzotriazole or 1-phenyl-5-mercaptotetrazole as described in, for example, L. F. A. Mason; Photographic Processing Chemistry, page 40, Focal Press (1975) but, on the contrary, the progress of development is greatly restrained by the presence of such an aldehyde, whereby the sensitivity of silver halide emulsions is greatly reduced. However, in high temperature rapid processing (e.g., 28.degree.-38.degree. C., 25 sec.), the addition of such a strong antifoggant results in a problem in that the composition of the developer is considerably changed with the passage of time by aerial oxidation, etc., the change in the compositions of photographic materials, etc., which changes greatly the photographic properties.
Also, an attempt of adding alkylene oxides to ordinary silver halide photographic emulsions to minimize the development processing dependence of the photographic emulsions cannot practically be employed since the addition of alkylene oxides greatly reduces the sensitivity of the silver halide emulsions.